I built 6 saw horses to Renn's design, which are the best I have ever seen and a very efficient use of standard length lumber. The plywood is Superply from Roseburg Forest Products, which is available locally (Portland, Oregon) and relatively cheap. The 20' LVL is a Microlam from Weyerhauser.

 

This was all started on July 4th, 2005 in a carport and an old one car garage. An 18' canoe built nearly 20 years ago hangs from above on the diagonal in order to keep it under cover. This space is far from ideal, but it is the space I have. So if I want a 24' boat, I just have to wing it rather than over-analyze the working conditions.